PITCH IMPERFECT: Zack Wheeler makes what could be his next-to-last start for Triple-A Las Vegas on Friday night in Tacoma, Wash., pitching brilliantly through the first four innings, before getting roughed up a bit in the fifth. Photo: John Patzer

TACOMA, Wash. — Not everyone can explode onto the scene a la Matt Harvey. Most newcomers experience some growing pains upon getting The Call.

Not to be too much of a buzz kill, but more often than not, highly touted prospects fail to turn into highly accomplished major leaguers.

It is a sentiment the Mets and their fans should repeat 15 times a day between now and June 18, when Zack Wheeler is expected to make his major league debut. It’s a thought a Mets alumnus offered late Friday night here at Cheney Stadium.

“I think [they’ve] got to be careful how much hype they give the guy,” Howard Johnson, now the hitting coach for the Mariners’ Triple-A Tacoma affiliate, said following Wheeler’s most recent start for Las Vegas. “He’s just a kid. Going in that situation up there where it’s not good and expecting him to go in and just dominate, that can be tricky.”

HoJo, a 1986 Mets teammate of Wheeler’s current manager, Wally Backman, and the Mets’ hitting coach from 2007-10, saw his Rainiers struggle against the Mets’ jewel for four innings, only to erupt for three runs in the fifth, knocking Wheeler out of the game and denying him the win in a 12-5 Las Vegas blowout.

“I knew what I was doing wrong, but I couldn’t make the adjustment, which stinks as a pitcher,” said Wheeler, who explained that his front (left) shoulder was flying open. “It happens. It’s part of pitching. Learning experience.”

The Mets’ plan calls for Wheeler to make one last start for Vegas, and it is clear he isn’t a finished product. The 23-year-old has a 4.14 ERA in 12 starts totaling 63 innings, with 66 strikeouts and 25 walks. Break it down further, and he has a 5.88 ERA in his five home appearances, at hitters’ haven Cashman Field, and a 2.92 ERA in seven road games.

“He’s still got some work to do,” Johnson said. “But he might as well do it in the big leagues.”

“He’s still a young kid. Everybody’s going to get roughed up at some point,” Backman said. “But his stuff plays when he keeps the ball down in the zone. He’s just going to have to do that more consistently to be more effective in the big leagues. And I think he’s really capable.

“The more that he pitches, by holding him back as long as we’ve held him back, it’s been a plus for him. He’s learned from some of his mistakes.”

Everyone knows that finance largely has driven the Mets’ timing with Wheeler. By waiting until June 18, the Mets hope to ensure Wheeler will avoid “Super Two” status in the 2015-16 offseason (assuming he stays in the big leagues for good) and therefore couldn’t get a seven-figure 2016 salary through the arbitration process.

“It’s the business part of baseball,” Wheeler said.

In order to make such hypothetical technicalities relevant, Wheeler must polish his obviously impressive stuff. His fastball hit as high as 99 mph on the ballpark radar gun (which was calibrated in anticipation of Wheeler’s arrival) and accounted for six his seven strikeouts, yet Backman offered a better mix of pitches could help.

“You’ve got to be able to go back and forth,” Backman said. “He didn’t do that as much as he needed to [Friday].”

Said Johnson: “His secondary stuff wasn’t all that impressive.”

Wheeler’s game fell apart when his teammates sent nine batters to the plate in the top of the fifth, scoring five runs, and he couldn’t right himself mechanically.

“It was a long inning for him to wait,” Backman said. “But I’m not going to make any excuses for that. He’s got to be able to get past that.”

“Obviously, a long inning makes you sit a little longer,” Wheeler said. “It was a little more chilly [first-pitch temperature was 67 degrees], a bit more than we’re used to. But it’s no excuse. Just go out there, get a shutdown inning.”

Free advice to the Mets: Make sure Wheeler doesn’t suggest excuses during his postgame media session, even if he follows it up with, “But it’s no excuse.”

Wheeler swore he had no specific knowledge of his schedule, although he admitted, “You hear stuff. You can get excited. There’s nothing wrong with that.”

Debuting in Atlanta, the Georgia native said, “really doesn’t matter to me. Honestly. Obviously, there would probably be a lot of people there, but it won’t affect me. It’s people just watching.”

New York has been watching him since the Mets acquired him from the Giants nearly two years ago in exchange for Carlos Beltran. Maybe there will be an instant, Harvey-like payoff. Quite possibly not.

“He’ll still be able to get guys out, but not at the [dominant] way that’s being talked about,” Johnson said. “That’s the danger.”

The buzz lies in that danger, and in the upside that comes from averting it. It’s almost time for Wheeler to meet up with his hype. No matter the results, it’ll be worth watching.